Broadcast - 22 October 2023
Last technical night – As we had hoped, Lionel VK7ZLB, did indeed bring along his Icom 9700 transceiver. It was set up as a working rig, the antenna was replaced with suitable dummy loads, one incorporating an attenuated output to provide a “sniffer” level drive suitable for a frequency counter.
The frequency counter effectively demonstrate the drift of the rig as it heated up during transmit. The frequency incremented until the effect of the cooling fans’ activation eventually stabilized the temperature.
After transmitting the oscillator would cool down and was closer to the original frequency. When transmitting again this cycle repeated. Although the drift was technically only in the tens of Hertz which isn’t really a problem for voice it can present a problem when operating in digit modes.
The next step was to demonstrate the effect of using a GPS locked 10 MHz reference that was designed by George McLucas VK4AMG, connected to the external reference input of the 9700. This unit generates a reference output frequency when it acquires sufficient Global Positioning Satellites. However it soon became apparent we could not acquire any satellites from within the club room and consequently were unable to obtain a GPS lock. So the demonstration table was picked up and moved to an openable window. Within seconds of the GPS antenna being passed through the windows security mesh we had lock. With lock the frequency came back to within a Hertz or so of the desired frequency and was independent of transmit duration. Just as a side if you are using the GPS you also get the added nicety of having your Grid Locator displayed on the 9700.
This certainly proved to be an excellent visual example of the drift effect of crystal oscillators from heating and the advantage of using an external reference frequency for stability.
Lionel then took us through the theoretical process of a firmware upgrade. From the ICOM website through to the rigs SD card and the importance of backing up your rigs configuration data.
Firmware upgrading while certainly not hard, it is not for the faint hearted as an interruption could possibly result in a bricked rig. Lionel recommends the use of an Uninterruptible Power Supply or UPS so there is no chance of a power interruption. Like any software upgrades, during the final process “don’t touch anything, not just the touch screen but also physical knobs and controls as so many controls are now digitally interpreted by software and no longer directly varying the actual real life signal or parameter. Even when the screen stays blank, for that period that seems a little too long and you start to get edgy, remember patience, in reality it is only takes a couple of minutes.
The other external add-on, other than the frequency reference, that Lionel included in the demonstration was a PTT Extender. A PTT Extender relies on an Arduino decoding the rigs external control data stream to extract band information. The extender can then provide an active “Low” on one of its three outputs for designated 2m, 70cm and 23cm bands. The addition of this unit could allow, for example, the automatic switching between linear amplifiers depending on the rigs selected band. Lionel has already modified his kit to include optically isolated outputs rather than the original transistor coupled and also the increase in limit resistor value on the Tx and Rx front panel LEDs to decrease the brightness to a usable non blinding level. Rather than fully explaining the PTT Extender, Richard VK7ZBX and Justin VK7TW covered the unit and its use in depth during a REAST DATV night broadcast on the 12th of April this year. This is available on the REAST YouTube channel, search for “IC-9700 Breakout”, or the following link in the text version.
https://www.youtube.com/watch?v=IWlD0OZSzyQ
Both the 10 MHz external reference and the PTT Extender are available from the “City Of Brisbane Amateur Radio Society”, the link is also included in the text version.
https://brisbaneradiosociety.net/vk4amg-ref/
Friday Coffee Morning had a special treat this week. Nic VK7WW brought along his latest prototype he has been working on. This time it was a 40 Metre AM half watt transmitter and once again constructed in a repurposed video switcher case. The design is based on the original CW “Cent” transmitter but this time for voice as an AM transmitter. Nic soon had it set up and transmitting, the NTARC SDR soon confirmed the excellent off air quality. Evidently Nic has successful made mainland contacts with it. Thanks Nic and watch this space.
JOTA/JOTI for 2023 volunteers to assist still have time!
By the time you hear this on Sunday we will be half way through the two day event. If you would like to assist and volunteer some of your time you still have until 3pm. Just drop down to the Venue at the NTARC Club rooms, at the Rocherlea Scout Hall, Archer St, Rocherlea.
Or if you prefer, listen out and respond to any CQ JOTA calls as we may need local contacts to chat with the participants on air in case we can’t link up to other Scout venues.
NTARC Auction Hosting - Well, we have all had five weeks to think about a “Shack Clear-out” auction and the possible items we want to re-home. Remember, this auction will be open to all amateurs not just NTARC members! Last broadcast we proposed Saturday the 25th November to work with. So now it’s up to you. By that I mean you have two weeks to send in your expressions of interest with a rough guess as to what you would like to auction and the number of items or boxes.
Please let Idris, VK7ZIR or the club Secretary know by e-mailing secretary@ntarc.net. It only needs to be a quick note stating your name, call-sign and proposed number of items. Unless a reasonable number of sellers and items come forward to make it viable then the event will be postpone to next year and we will try again.
NTARC QSL Cards - Andrew VK7DW, our QSL manager has advised me that the following QSL cards are available for collection. VK7’s AT, BO, AU, GC, JFD, KPA, WW and ZR. If you just heard your call-sign then there are cards waiting at the NTARC club rooms for collection on the next Coffee morning or Technical Night. Thank you Herman for your continued support regarding QSL deliveries and thank you Andrew for the update.
As always equipment pictures and links are available on the NTARC Web site under “Blogs” for this broadcast. Now back to the house keeping.
UPCOMING EVENTS
The TestNet and TechNet session – Every Wednesday.
Coffee Morning - held every Friday in the NTARC Club rooms.
The Club Technical night - The next session will be on Wednesday the 1st of November, Club Rooms.
That’s all folks,
73 from Stefan, VK7ZSB, Secretary NTARC Inc.
